/Engine/Source/Runtime/ApplicationCore/Public/GenericPlatform/GenericPlatformInputDeviceMapper.h
This is useful for functions such asFGenericApplicationMessageHandler::OnControllerAnalogthat used to use the "int32 ControllerId" as a parameter so that you can call the newFGenericApplicationMessageHandlerthat take in a PlatformUserId and an InputDeviceId.
True if this maps to a real user
bool RemapControllerIdToPlatformUserAndDevice ( int32 ControllerId, [FPlatformUserId](API\Runtime\Core\Misc\FPlatformUserId) & InOutUserId, [FInputDeviceId](API\Runtime\Core\Misc\FInputDeviceId) & OutInputDeviceId )